/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2006, University of Maryland
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.classfile.impl;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;

import edu.umd.cs.findbugs.FindBugs;
import edu.umd.cs.findbugs.classfile.ClassDescriptor;
import edu.umd.cs.findbugs.classfile.ICodeBaseEntry;
import edu.umd.cs.findbugs.classfile.ICodeBaseIterator;
import edu.umd.cs.findbugs.classfile.ICodeBaseLocator;
import edu.umd.cs.findbugs.classfile.IScannableCodeBase;
import edu.umd.cs.findbugs.classfile.InvalidClassFileFormatException;
import edu.umd.cs.findbugs.classfile.ResourceNotFoundException;
import edu.umd.cs.findbugs.classfile.analysis.ClassNameAndSuperclassInfo;
import edu.umd.cs.findbugs.classfile.engine.ClassParser;
import edu.umd.cs.findbugs.classfile.engine.ClassParserInterface;
import edu.umd.cs.findbugs.io.IO;

/**
 * Implementation of ICodeBase for a single classfile.
 *
 * @author David Hovemeyer
 */
public class SingleFileCodeBase implements IScannableCodeBase {

	private ICodeBaseLocator codeBaseLocator;
	private String fileName;
	private boolean isAppCodeBase;
	private int howDiscovered;
	private long lastModifiedTime;
	private boolean resourceNameKnown;
	private String resourceName;

	public SingleFileCodeBase(ICodeBaseLocator codeBaseLocator, String fileName) {
		this.codeBaseLocator = codeBaseLocator;
		this.fileName = fileName;
		this.lastModifiedTime = new File(fileName).lastModified();
	}

	@Override
    public String toString() {
		return fileName;
	}
	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#getCodeBaseLocator()
	 */
	public ICodeBaseLocator getCodeBaseLocator() {
		return codeBaseLocator;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.IScannableCodeBase#containsSourceFiles()
	 */
	public boolean containsSourceFiles() throws InterruptedException {
		return false;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.IScannableCodeBase#iterator()
	 */
	public ICodeBaseIterator iterator() throws InterruptedException {
		return new ICodeBaseIterator() {
			boolean done = false;

			/* (non-Javadoc)
			 * @see edu.umd.cs.findbugs.classfile.ICodeBaseIterator#hasNext()
			 */
			public boolean hasNext() throws InterruptedException {
				return !done;
			}

			/* (non-Javadoc)
			 * @see edu.umd.cs.findbugs.classfile.ICodeBaseIterator#next()
			 */
			public ICodeBaseEntry next() throws InterruptedException {
				if (done) {
					throw new NoSuchElementException();
				}
				done = true;
				return new SingleFileCodeBaseEntry(SingleFileCodeBase.this);
			}
		};
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#lookupResource(java.lang.String)
	 */
	public ICodeBaseEntry lookupResource(String resourceName) {
		if (!resourceName.equals(getResourceName())) {
			return null;
		}

		return new SingleFileCodeBaseEntry(this);
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#setApplicationCodeBase(boolean)
	 */
	public void setApplicationCodeBase(boolean isAppCodeBase) {
		this.isAppCodeBase = isAppCodeBase;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#isApplicationCodeBase()
	 */
	public boolean isApplicationCodeBase() {
		return isAppCodeBase;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#setHowDiscovered(int)
	 */
	public void setHowDiscovered(int howDiscovered) {
		this.howDiscovered = howDiscovered;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#getHowDiscovered()
	 */
	public int getHowDiscovered() {
		return howDiscovered;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#setLastModifiedTime(long)
	 */
	public void setLastModifiedTime(long lastModifiedTime) {
		if (lastModifiedTime > 0 && FindBugs.validTimestamp(lastModifiedTime)) {
			this.lastModifiedTime = lastModifiedTime;
		}
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#getLastModifiedTime()
	 */
	public long getLastModifiedTime() {
		return lastModifiedTime;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#getPathName()
	 */
	public String getPathName() {
		return fileName;
	}

	InputStream openFile() throws IOException {
		return new BufferedInputStream(new FileInputStream(fileName));
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.ICodeBase#close()
	 */
	public void close() {
		// Nothing to do
	}

	/**
	 * Get the resource name of the single file.
	 * We have to open the file and parse the constant pool
	 * in order to find this out.
	 *
	 * @return the resource name (e.g., "java/lang/String.class"
	 *          if the class is java.lang.String)
	 */
	String getResourceName() {
		if (!resourceNameKnown) {
			// The resource name of a classfile can only be determined by reading
			// the file and parsing the constant pool.
			// If we can't do this for some reason, then we just
			// make the resource name equal to the filename.

			try {
				resourceName = getClassDescriptor().toResourceName();
			} catch (Exception e) {
				resourceName = fileName;
			}

			resourceNameKnown = true;
		}
		return resourceName;
	}

	ClassDescriptor getClassDescriptor() throws ResourceNotFoundException, InvalidClassFileFormatException {
		DataInputStream in = null;
		try {
			try {
				in = new DataInputStream(new BufferedInputStream(new FileInputStream(fileName)));
				ClassParserInterface classParser = new ClassParser(in, null, new SingleFileCodeBaseEntry(this));
				ClassNameAndSuperclassInfo.Builder builder = new ClassNameAndSuperclassInfo.Builder();

				classParser.parse(builder);

				return builder.build().getClassDescriptor();
			} finally {
				if (in != null) {
					IO.close(in);
				}
			}
		} catch (IOException e) {
			// XXX: file name isn't really the resource name, but whatever
			throw new ResourceNotFoundException(fileName);
		}
	}

	/**
	 * Return the number of bytes in the file.
	 *
	 * @return the number of bytes in the file, or -1 if the file's length
	 *          can't be determined
	 */
	int getNumBytes() {
		File file = new File(fileName);
		// this is not needed but causes slowdown on a slow file system IO
		// file.length() returns zero if not found, and matches the contract of this method
//		if (!file.exists()) {
//			return -1;
//		}
		return (int) file.length();
	}
}
